In one respect, this invention is related to solar control film adapted for bonding to windowpanes. In another aspect, the invention relates to a method of manufacturing solar control films.
It has long been recognized that a transparent or translucent film could be coated with a thin transparent-reflective metallic layer and used to control the solar radiation entering a room. For example, Lion U.S. Pat. No. 2,774,421 discloses roller-mounted window shades in which a transparent or translucent film is coated with a thin layer of vapor-deposited aluminum which may in turn be overcoated with a protective lacquer or varnish. While effective to a degree, Lion's window shade is spaced from the inner surface of a windowpane, thus permitting a considerable amount of heat to be admitted into the room.
Antonson et al U.S. Pat. No. 3,290,203 discloses a solar control film which, like Lion's, utilizes a transparent film which is metallized with a transparent-reflective aluminum layer on one face and provided with a protective overcoating. In the Antonson et al product, however, a water-activatible adhesive is employed to bond the solar control film directly to the inner surface of a windowpane, thereby greatly reducing the amount of solar energy which would otherwise enter the room, be absorbed by objects therein, and be re-emitted as heat. Another type of water-activated adhesive is shown in Theissen U.S. Pat. No. 3,681,179, where a normally tacky and pressure-sensitive adhesive is coated over the film and temporarily inacitivated by an overcoating of a water-soluble material. In both the Antonson et al and Theissen products, water is applied to the exposed coated surface, the windowpane (or both), the film placed in contact with the window and slid into position, and a squeegee thereafter being used to ensure intimate contact between the film and the windowpane. While both the Antonson et al and Theissen products have enjoyed widespread commercial success, there has been a desire for a solar control film product which could be utilized during the hot summer months and removed during the cold winter months. Although both the Antonson et al and Theissen solar control films can be removed, the process of removal is likely to destroy or distort them so that they cannot thereafter be easily reapplied.
For several years, various types of removable and replaceable solar control film have been available in the marketplace. In one embodiment, the solar control film has been simply a metallized biaxially oriented polyethylene terephthalate film in which the metallized layer is overcoated with a "cling" adhesive consisting essentially of a solvent-soluble polyester adhesive. In another embodiment, the "cling" adhesive is a plasticized vinyl film laminated to the structure by means of the soluble polyester adhesive. In the latter product, the structure adheres to a windowpane because of the plasticizer which exudes from the vinyl polymer and forms almost a monomolecular layer between the solar control film and the windowpane. While both types of product are easily applied and can be removed after being adhered to a windowpane for a comparatively short period of time, long-term exposure results in an adhesion buildup such that the solar control film is prone to distortion upon removal, effectively preventing it from being re-applied. Additionally, laminated products of the second type require both a coating and a laminating step, increasing the cost of manufacture.